Rapidly moisture-curable polyethylene formulation

Abstract

A moisture-curable polyethylene formulation comprising a (hydrolyzable silyl group)-functional polyethylene copolymer and a condensation cure catalyst. The formulation is designed to be rapidly moisture curable under ambient conditions. Also methods of making and using same; cured polymer products made therefrom; and articles containing or made from same.

The invention claimed is: 
     
       1. A moisture-curable polyethylene formulation comprising from 15 to 99.99 weight percent (wt %) of (A) a (hydrolyzable silyl group)-functional polyethylene copolymer (HSG-FP Copolymer); from 0.01 to 5 wt % of (B) a condensation cure catalyst; and from 0 to 84.99 wt % of one or more optional additives; with the proviso that when (B) is only a dialkyltin dicarboxylate, the dialkyltin dicarboxylate is at least 0.10 wt % and the (A) HSG-FP Copolymer is at most 99.90 wt % of the moisture-curable polyethylene formulation; wherein all wt % are based on total weight and add to 100.00 wt % of the moisture-curable polyethylene formulation; and wherein the (A) HSG-FP Copolymer is made by copolymerizing ethylene, at least one alkenyl-functional hydrolyzable silane, optionally propylene, the copolymerizing being done under effective process conditions in a high-pressure-and-temperature (HPT) reactor free of a metal-containing olefin polymerization catalyst and containing an organic peroxide and the copolymerizing is free of an optional olefinic comonomer selected from an olefinically-unsaturated carboxylic acid, an olefinically-unsaturated carboxylic ester, an olefinically-unsaturated carboxylic anhydride, and combinations thereof and, optionally, a chain transfer agent (CTA) that is not propylene or a (C 4 -C 20 )alpha-olefin; and wherein the (A) HSG-FP Copolymer is characterized by a total hydrolyzable silyl group content from 0.38 to 0.99 mole percent (mol %) and a molecular mass dispersity of any one of limitations (i) to (iii): (i) a ratio of absolute z-average molecular weight to absolute weight-average molecular weight (M z(abs) /M w(abs)  or absolute molecular mass dispersity) of 9.51 or greater; (ii) a ratio of absolute molecular mass dispersity to conventional molecular mass dispersity ((M z(abs) /M w(abs) )/(M w(conv) /M n(conv) ) of 1.51 or greater, wherein M w(conv)  is conventional weight-average molecular weight and M n(conv)  is conventional number-average molecular weight; and (iii) both (i) and (ii); wherein the (B) condensation cure catalyst comprises a dialkyltin dicarboxylate or a sulfonic acid of formula RSO 3 H wherein R is (C 1 -C 10 )alkyl, (C 6 -C 10 )aryl, a (C 1 -C 10 )alkylsubstituted (C 6 -C 10 )aryl, or a (C 6 -C 10 )aryl-substituted (C 1 -C 10 )alkyl. 
     
     
       2. The moisture-curable polyethylene formulation of  claim 1  characterized by any one of limitations (i) to (xii): (i) the HPT reactor and process of making the (A) HSG-FP Copolymer is free of propylene and the (A) HSG-FP Copolymer is free of propylenic units derived from propylene, (ii) the HPT reactor and process of making the (A) HSG-FP Copolymer comprises from greater than 0 wt % to at most 2 wt % of propylene, based on total mass flow rates of ethylene, at least one alkenyl-functional hydrolyzable silane, and propylene into the HPT reactor and the (A) HSG-FP Copolymer comprises from >0 wt % to at most 2 wt % of propylenic units derived from propylene, (iii) the HPT reactor and process of making the (A) HSG-FP Copolymer is free of (C 4 -C 20 )alpha-olefin and the (A) HSG-FP Copolymer is free of units derived from the (C 4 -C 20 )alpha-olefin, (iv) the HPT reactor and process of making the (A) HSG-FP Copolymer comprises from >0 wt % to at most 20 wt % of (C 4 -C 20 )alpha-olefin, based on total mass flow rates of ethylene, at least one alkenyl-functional hydrolyzable silane, and (C 4 -C 20 )alpha-olefin and the (A) HSG-FP Copolymer comprises from >0 wt % to at most 20 wt % comonomeric units derived from the (C 4 -C 20 )alpha-olefin, (v) both (i) and (iii), (vi) both (i) and (iv), (vii) both (ii) and (iii), (viii) both (ii) and (iv), (ix) the (A) HSG-FP Copolymer is free of grafted hydrolyzable silyl groups and the moisture-curable polyethylene formulation is free of alkenyl-functional hydrolyzable silane, (x) both (ix) and any one of limitations (i) to (viii), (xi) the effective process conditions comprise a reactor temperature from 175° to 400.0° C. and a reactor pressure from 34.5 to 344.7 megapascals, or (xii) both (xi) and any one of limitations (i) to (x). 
     
     
       3. The moisture-curable polyethylene formulation of  claim 1 , wherein the total hydrolyzable silyl group content of the (A) HSG-FP Copolymer is from 0.43 to 0.99 mol %. 
     
     
       4. The moisture-curable polyethylene formulation of  claim 1 , wherein the molecular mass dispersity of the (A) HSG-FP Copolymer is characterized by any one of limitations (i) to (iv): (i) a ratio of M z(abs) /M w(abs)  of 10.5 to 21.0; (ii) a ratio of (M z(abs) /M w(abs) )/(M w(conv) /M n(conv) ) of 1.9 to 3.4; (iii) both (i) and (ii); (iv) a ratio of M z(abs) /M w(abs)  of 16.2 to 18.9 and a ratio of (M z(abs) /M w(abs) )/(M w(conv) /M n(conv) ) of 2.3 to 3.1. 
     
     
       5. The moisture-curable polyethylene formulation of  claim 1 , wherein each hydrolyzable silyl group of the (A) HSG-FP Copolymer is independently a monovalent group of formula (R 2 ) m (R 3 ) 3-m Si—, wherein subscript m is an integer of 1, 2, or 3; each R 2  is independently H, HO—, (C 1 -C 8 )alkoxy, (C 2 -C 6 )carboxy, phenoxy, (C 1 -C 6 )alkyl-phenoxy, (C 1 -C 6 )alkyl(H)N—, ((C 1 -C 6 )alkyl) 2 N—, (C 1 -C 6 )alkyl(H)C═NO—, or ((C 1 -C 6 )alkyl) 2 C═NO—; and each R 3  is independently (C 1 -C 8 )alkyl or phenyl. 
     
     
       6. The moisture-curable polyethylene formulation of  claim 1  comprising a total of from >0 wt % to 84.99 wt % of the one or more optional additives, wherein the additive(s) is/are selected from additives (C) to (I): (C) an antioxidant; (D) a colorant; (E) a moisture scavenger; (F) a stabilizer for stabilizing the formulation against effects of ultraviolet light (UV stabilizer), such as a hindered amine light stabilizer (HALS); (G) a processing aid; (H) a flame retardant; (I) a polymer that is not (A); and a combination of any two or more of (C) to (I).